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Cleaner Air Tied to Healthier Lungs in Kids

At a Glance

Falling air pollution levels in Southern California were associated with improvements in children’s lung function during a critical period of growth and development.

The results highlight the potentially long-term effects of air quality on human health.

Better air quality over the past 20 years has helped reduce lung problems in Southern California.Ryan McVay/Photodisc/Thinkstock

Over the past 30 years, researchers have linked a wide array of health effects to air pollution. Among these are reduced lung function, asthma, cardiovascular disease, preterm birth, and even death. The period between 11 and 15 years of age is particularly important for long-term lung function, as lungs are developing rapidly.

In Southern California — long known for its levels of air pollution — public policies have helped to improve air quality over the past few decades. A team of researchers led by Dr. W. James Gauderman of the University of Southern California used these changes to examine the association between air quality improvements and children’s lung function.

The team used data from the 20-year Children’s Health Study, which took measurements of children’s health and outdoor air pollution levels in communities throughout Southern California. The researchers examined data from 3 different groups of children taken during the time periods 1994–1998, 1997–2001, and 2007–2011. Numbering over 2,100, the children came from 5 communities: Long Beach, Mira Loma, Riverside, San Dimas, and Upland. All received 2 or more tests of lung function from the ages of 11 to 15 years old. The scientists compared lung function with levels of nitrogen dioxide, ozone, and particulate matter of different sizes. The study was funded by NIH’s National Institute of Environmental Health Sciences (NIEHS) and others. Results appeared on March 5, 2015, in New England Journal of Medicine.

The researchers found improvements in lung function development were associated with declining levels of nitrogen dioxide; fine particles, which are 2.5 micrometers in diameter or less (found in smoke and haze); and larger particles with diameters up to 10 micrometers (including wind-blown dust). The proportion of children with clinically low lung function at 15 years of age also declined as air quality improved. Across the 3 time periods, the proportion with low lung function fell from 7.9% to 6.3% to 3.6%. These associations held after adjustment for several other variables, including smoking habits, health insurance, parental education, and exposure to cats, dogs, mold, and mildew.

The effects of the 3 different pollutants couldn’t be separated, as their levels were highly correlated. However, these results show that broad-based efforts to improve general air quality can significantly improve lung function in children. Improvements were seen in both boys and girls, in children with and without asthma, and in children of different racial/ethnic backgrounds.

“We expect that our results are relevant for areas outside Southern California, since the pollutants we found most strongly linked to improved health—nitrogen dioxide and particulate matter—are elevated in any urban environment,” Gauderman says.

The researchers note that these results and others suggest that further improvements to air quality could lead to even better lung health.